Beyond Third Generation mobile communication system (Beyond Third Generation mobile communication system, B3G) is named International Mobile Telecommunications Advanced (IMT-Advanced) by the International Telecommunication Union Radio (International Telecommunication Union Radio, ITU-R). The IMT-Advanced imposes high requirements on the system capacity. Nevertheless, the high-bandwidth spectrum that supports the high capacity of the IMT-Advanced is generally available in higher bands, but higher bands involve great path loss and penetration loss, and can hardly achieve good coverage.
To meet the requirements of the IMT-Advanced with respect to system capacity and coverage, the prior art introduces a relay technology to improve the system capacity and coverage. In a traditional network, the wireless connection between a base station and a User Equipment is a direct wireless connection, which forms a single-hop network. The relay technology is intended to add one or more relays between the base station and the User Equipment. The relays are responsible for processing and forwarding radio signals sent by the base station at one or more attempts until the User Equipment receives the radio signals. Taking the simple 2-hop relay as an example, a radio link between base station and a User Equipment is split into two radio links, namely, a radio link from the E-UTRAN NodeB to a Relay Node, and a radio link from the Relay Node to the User Equipment, thus making it possible to replace a low-quality link with two high-quality links and achieve higher link capacity and better coverage.
FIG. 1 shows a network topology in which the relay technology is introduced. The network includes a Mobility Management Entity (MME), a base station (e.g. E-UTRAN Node B, eNB), an Relay Node (Relay Node, RN), and a control base station (e.g. Donor E-UTRAN NodeB, DeNB) of the RN. The DeNB is also an base station, and provides a function of controlling the RN in addition to conventional functions of an eNB. The RN may be fixed or mobile. When the RN is mobile, the DeNB that controls the RN is also variable.
In FIG. 1, the interface between the MME and the eNB is S1, and the interface between the MME and the DeNB is also S1. An X2 interface may exist between the eNB and the DeNB or not. No direct interface exists between the RN and the eNB. A wireless Un interface exists between the RN and the DeNB. The coverage of the eNB and the DeNB may be divided into multiple different cells. When a connected User Equipment moves from a cell of the eNB to a cell of the DeNB, a handover process will be triggered. Like the eNB and DeNB, the RN is equivalent to an base station. The coverage of the RN may also be divided into different cells. When a connected UE moves from a cell of the eNB to a cell of the RN, a handover process will be triggered.
In the process of researching and practicing the prior art, the inventor of the present invention finds that in the prior art, when the User Equipment (User Equipment, UE) hands over from the eNB to the RN, the UE can interact with the RN to obtain the identity of the RN cell (RN_PCI), and report the RN_PCI to the network. According to the RN_PCI, the network determines the RN to which the UE will hand over, but the network is unable to determine the control base station that controls the RN, and unable to send a Handover_Request message to the correct DeNB. Consequently, the handover process cannot proceed normally.